An integrated circuit (IC) is a semiconductor device containing many small, interconnected components. These components function together to enable the IC to perform a task, such as control an electronic device, or perform logic operations. ICs are found in computers, cellular telephones, and many other electronic devices.
ICs and other semiconductor devices typically comprise multiple layers. The connections between the layers are known as vias. In integrated circuit design, a via is a small opening in an insulating oxide layer that allows a conductive connection between different layers of an IC. Multiple vias may be coupled together to connect one conductive region in an IC to another conductive region in the same or an adjacent IC.
Vias are subject to manufacturing errors. When a manufacturing error occurs in a via, the via may not conduct properly and thus may prohibit an IC from functioning correctly. Therefore, the testing of via structures is an important aspect of IC production and reliability.
Via related leakage and breakdown is one of the top issues for back end of the line (BEOL) process development and reliability. Traditional via testing structures such as via-comb (FIG. 1) and intertwined via chains (FIG. 2) are not capable of precisely diagnosing the root cause of a via related issue (in FIGS. 1 and 2, M1, M2 are metal layers, V1 are vias). For example, such structures are not capable of separately analyzing and differentiating between via leakage/breakdown problems occurring at the top of a via from via leakage/breakdown problems occurring at the bottom of a via. Such information is critical for process development, especially for self-aligned contact processes. In addition, such via testing structures are incapable of electrically identifying via overlay problems and cannot differentiate via-line versus line-line leakage and/or breakdown.